This invention is an improved inner ram seal for a blowout preventer type valve, useful on wellheads, which may be actuated to seal on a like seal in an opposing preventer ram or on wireline passing through the preventer, closing the well.
U.S. Pat. No. 4,265,424 to Jones and U.S. Pat No. 4,323,256 to Miyagishima show examples of ram seals configured to seal around pipes passing through a blowout preventer.
The inner seals used in the wireline blowout preventer rams of U.S. Pat. No. 4,214,605 to Hardgrave and U.S. Pat. No. 4,325,534 to Roark and Hayter seal around wireline and have been found not capable of sealing when well pressures below the closed rams are in the 15,000 to 20,000 psi range. These ram assemblies also require attachment of guides to each ram to cam the wireline into a small sealing area in the middle of the inner seal sealing face, between notches in the upper and lower inner seal retainer plates. Guide edges dragging across wire as the preventer is closing abrade and may damage the wire. As sealing material does not extend from the retainer plates on these inner seals, providing a large seal surface, the wireline must be inside narrow retainer plate notches when the rams are closed to allow only the resilient sealing material to contact the wire and not the metal seal retainer plates, which would easily damage or cut the wire passing through the blowout preventer.